So I want to make a mast beacon lightning arrestor...

[Gewehr98]

Alright, APS gurus, I'm running into a mental block with what should be an easy fix.

After our move to the new house out here in the countryside, I delayed putting up my weather station until I had everything ready again.

The 20 foot mast carries the signals from the anemometer and windvane on the top down to the wireless transmitter at the base via an internal cable.

The wireless transmitter adds a humidity sensor and thermometer to the wind/velocity data, as well as a rainfall gage, and transmits it all to the indoor console.

Problem is, in the previous location, it took a lightning strike or two.  It came back to life by removing the batteries from the transmitter and resetting, thank goodness.

Now I’m adding a small flashing LED beacon to the top of the mast, not as much an aircraft avoidance thing as a visual during bad storms and snow.  It’s a super-bright LED 12vdc flasher, so now I’ll be running 12v inside the mast.

I have a small 12 volt wall wart feeding it from the covered outside outlet.

Here’s my plan - I want to protect the circuit and/or household 115vac wiring from a lightning strike, so in addition to the ground strap attached to the mast, I should add a lightning arrestor circuit in line with the LED’s 12v power.

I have a MOV that I can wire between one side of the 12v power and ground strap, but wouldn’t one or two 12v fast-blow fuses on both the + and – 12 volt sides keep things from melting down, too?

I see all sorts of ham radio lightning arrestors, but nothing for mast beacons.  This shouldn’t be difficult to design and implement, but I’m not familiar with any voltage-based surge suppression save for power strips and UPS units. 

What say you people - am I on the right track?

[RevDisk]

Uhm. Forgive me if I am missing something, but why not just put a grounded lightning rod on it?

http://www.lightningrodsupply.com/index_files/page0001.htm

For the cables, if you really want, you could add an In-Line Fuse Holder.

[AZRedhawk44]

Can't you fuse the outlet the wall-wart plugs into?  Or turn it into a GFCI outlet?

I bet that if your mast beacon were hit by a lightning bolt, your wall-wart would turn into a charred brick of plastic and silica in 0.00001 seconds and whatever circuit it's wired into for your house would just pop open.  But isolating it further with either conversion to a GFCI outlet or insertion of a fuse on that particular outlet would stop a lightning strike from moving upstream in your house.

[geronimotwo]

attach a lightning rod to the highest point in your area, rather than your observation mast.  why give the potential for more strikes on your sensitive equipment?

[Gewehr98]

My weather station mast is the highest thing on my property, by a good 10 feet.

I have the 20 foot mast mounted to the back deck on the north side of the house so that the windvane and anemometer can see the wind from all directions, without the roof blocking the wind from the south.

The mast itself is grounded by strap and ground rod, so if it takes a hit, that's all well and good. 

What bothers me is that the LED beacon I'm installing is the tallest part of the mast.

I see what RevDisk is saying, I could add a lightning rod on an offset mount to the mast, so that it's at least marginally taller than the beacon and instruments.

The outlet that the wall wart is plugged into is already GFCI protected, so there's a small safety factor there. 

Or I could let it get zorched and ask spousal unit for a better weather station (I want one with the web reporting) for Christmas...   

[RocketMan]

Took a feather lightning strike on my tri-bander years ago in COS.  Went down the ground strap (left an arc mark on some metal flashing on a corner it went around) into the ground via an eight foot ground rod.  Came back out of the ground via another ground rod and into the ham shack.  Fried some computer gear attached to that ground.  (All antenna and power entries into the ham shack had been disconnected prior to the storm.)
Also cooked a telephone and microwave connected to the house AC ground.
Something to think about.

High speed semiconductor protection fuses might be worth considering.  Put two of those in both sides of the 12Vdc lines, close to their exit point from the mast.  MOVs to ground from both sides.  Maybe even some fast, high current diodes in reverse from both sides to ground.

[Azrael256]

GFCI will do zippitee-doo-dah against a lightning strike.

I take that back.  It will pop, sizzle, and burn with a green flame.  Assuming it trips before bursting into flames (unlikely), the gap in the switch is approximately one gajillionth of one percent of the miles the bolt travelled to get to you.  GFCI is cool for when a bad windstorm tears up your gear and then soaks it.

Your problem is that you're not protecting an antenna (like the HAMs), but a load at the top of a lightning rod.  Either isolate the load (would it run on a battery?) from the spark-gap protected pole (I'm assuming its an antenna, but I dunno) or do your best to make a more attractive target elsewhere.  A spark gap to ground in your power circuit might help you, but you risk everything to the meter.

The pole is isolated from the deck, right?

Think Raspberry Pi for a DIY station with whatever reporting you like.  Its how I built mine.

[Gewehr98]

That's an elegant way to put it, but very true.  It is an electrical load at the top of a very tall lightning rod.  It's mounted to the deck's wooden structure with pipe clamps and lag screws. 

The mast is just two 10-foot sections of galvanized steel pipe, normally used for chain link fences.  I chose it for my weather station instruments because it's got enough wall thickness to not whip too badly in strong winds. 

A small 12v battery, say a 12v, 7Ah battery used in an UPS unit, would certainly drive the LED beacon.  That still leaves me with a charging circuit, unless I figure out a solar panel that can charge it enough on a daily basis and mount that on the mast.

Maybe a wall wart charger that's on a timer circuit, with an additional solid-state relay (love those things, bought a bunch of 'em!) cutting things out at night so the battery and LED would be somewhat stand-alone? A lightning strike during the daytime charging cycle...

I was also considering a small 115vac isolation transformer for the AC side of the 12v wall wart.  I don't know if the isolation transformer's internal windings and insulation would survive a lightning strike any better than the windings of the wall wart, though. 

If I tie a couple MOVs from both the + and - sides of the 12v connection at the LED's location topside directly to the steel mast, maybe that would convince the lightning to take the easier route through the ground strap to the ground rod? 

[zxcvbob]

http://www.northerntool.com/shop/tools/product_200578631_200578631

(and I'm pretty sure neon lamps are faster and can handle more current than MOV's)

[RevDisk]

That's an elegant way to put it, but very true.  It is an electrical load at the top of a very tall lightning rod.  It's mounted to the deck's wooden structure with pipe clamps and lag screws. 

The mast is just two 10-foot sections of galvanized steel pipe, normally used for chain link fences.  I chose it for my weather station instruments because it's got enough wall thickness to not whip too badly in strong winds. 

A small 12v battery, say a 12v, 7Ah battery used in an UPS unit, would certainly drive the LED beacon.  That still leaves me with a charging circuit, unless I figure out a solar panel that can charge it enough on a daily basis and mount that on the mast.

Maybe a wall wart charger that's on a timer circuit, with an additional solid-state relay (love those things, bought a bunch of 'em!) cutting things out at night so the battery and LED would be somewhat stand-alone? A lightning strike during the daytime charging cycle...

http://www.mcmelectronics.com/product/VELLEMAN-SA-SOL4UCN2-/28-11138
http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-28-11153-/28-11153#description

And a normal car battery. Or rather, I'd recommend motorcycle battery. Better, two of them, on opposite sides of the pole. Put the entire package in one place. 

[Azrael256]

Solar would be really good.

If you have a path to ground with the household circuit in the way, expect fireworks.  A solid state relay to shut off a wall wart is cool, but may not help.  Look at the datasheet for the line "dielectric strength" and compare with the voltage of a lightning strike.  It's debatable, but something in MV is generally accepted.  

Arresters frequently use whatever the resistance is of 6" of air (the strike is expected to jump the gap), so any kind of part that uses micron-scale switching isn't up to the task.

So, solar will give you really good isolation (or the ability to set it up, anyway), but the lighting circuit is fully sacrificial.  An arrester on each of the power supply lines to the light might work (some come as packages that cover hot/neutral or pos/neg together) but failure means an insurance claim.  A MOV/SOV is a good bet if you go that way. Look for a place that sells water well equipment.

Pro tip: If you buy from MCM, set up an online account, put the gear you want in your shopping cart, and then let it sit for a week.  Half the time they'll send a 10% off coupon if you do.

[charby]

what about this?

http://www.boatersland.com/lli-ll-sbl.html?gclid=CKbP6MiPsrkCFc4-MgodQy4AAA

[zxcvbob]

what about this?

http://www.boatersland.com/lli-ll-sbl.html?gclid=CKbP6MiPsrkCFc4-MgodQy4AAA

That's too easy.  (Killjoy)   

[charby]

That's too easy.  (Killjoy)   

sometimes it just takes a simple google search. :)

[RevDisk]

what about this?

http://www.boatersland.com/lli-ll-sbl.html?gclid=CKbP6MiPsrkCFc4-MgodQy4AAA

This. Unless you want something bigger and brighter.

[Gewehr98]

Actually, smaller with less weight.  That's massive compared to what I have already, and would increase the sway/whip of my weather station.

I wonder what's in these things?  2x MOVs?

http://www.ebay.com/itm/150659640811?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[Gewehr98]

The beacon I have for mounting topside:

http://www.ebay.com/itm/221144715473?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[charby]

smaller?

http://www.meritline.com/bicycle-bike-bright-red-led-tail-light-solar-energy-rechargeable-adjustable-clamp---p-62728.aspx

[charby]

a few mods and this would work

http://www.gardenandponddepot.com/solar-lights/384-solar-led-red-driveway-marker-stake-light.html

[Gewehr98]

That's neat, Charby!

I wonder if it's weatherproof?

[Gewehr98]

I have two of those driveway marker lights, albeit in blue.

They suck - very dim lights, and they won't charge enough to last a full night, even in summertime.   

[charby]

That's neat, Charby!

I wonder if it's weatherproof?

bike or driveway marker?

Also if you go with your original light check this out for building your own solar battery bank.

http://www.instructables.com/id/9V-Solar-Battery-Charger/

[Gewehr98]

Bike light.  Tiny, but self-contained.

I'm grabbing a spare 12v 7Ah UPS battery and wiring it in to an ammeter and the beacon to see what it draws. 

Solar would be good, as long as the panel is mounted near the base of the mast.

[never_retreat]

The proper tool would be Austin Ring transformer.

[zxcvbob]

That looks like the whole tower is standing on insulators.  I'm not so sure the ring transformer is for lightning protection (although the spark gap bypassing it will do so)